<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
<title></title>
</head>
<body>
<script type="text/javascript">
    var BMI = 23;
    var result = "";
    if(BMI < 20){
        result = "体重过轻";
    }else if(BMI >= 20 && BMI < 25){
        result = "体重适中";
    }else if(BMI >= 25 && BMI < 30){
        result = "体重过重";
    }else if(BMI >= 30 && BMI < 35){
        result = "肥胖";
    }else{
        result = "非常肥胖";
    }
    document.write("BMI："+BMI);
    document.write("<br>结果："+result);
</script>
</body>
</html>
